Studying Universe at extreme energies Print E-mail

ImageAn interview with Alessandro de Angelis, physicist at University of Udine and INFN in Trieste, Italian national coordinator for the MAGIC experiment, composed of two giant telescopes in the Canary Islands.

Why did you build a second MAGIC telescope?

We needed the stereo configuration for two reasons. First, to increase our sensitivity which is now more or less doubled. We can see more sources now, and we need a smaller observation time to detect variability. Second, to improve our angular resolution in a sense that we can now image many galactic sources. With just one telescope our spatial resolution was not good enough to really see the details of many galactic emitters. Making an image from which you can infer the morphology of the source is important. Now, MAGIC can spot the points from which the high energy cosmic rays are produced in the source. And we got some bonuses as well: with two telescopes the signal is much cleaner especially at low energies. Life is much easier for the analysis.

What was your personal science driver for MAGIC-II?

I like fundamental physics very much, in particular the questions that are difficult to address with accelerators. One of these is the test of fundamental symmetry that you can do by studying photons propagating through cosmological distances. There is the possibility to detect violations of the Lorentz invariance, by comparing the arrival times of photons of different energies produced in transients: if the speed of light turns out not to be constant, but dependent on energy, we are on top of a new physics – and MAGIC is the most sensitive instrument for this kind of study. The possibility to detect new particles in the vacuum, belonging to the family of the so-called axions, is another line of research that I am following. Those particles could mix to photons (i.e., photons transform into axion-like-particles and vice versa), and detecting this phenomenon would be a breakthrough in our understanding of the vacuum and of the energy of the Universe. All this requires the study of the deep Universe at extremely high energies. That’s very exciting!

How do you select your targets for MAGIC?

We go through a democratic procedure. There is a time allocation committee which evaluates the proposals. The good thing is that many of the proposals are signed by young people who have a strong motivation for selecting a target. Then there is a committee made by seniors evaluating which ideas are more worth to be pushed. On top of this there are the targets of opportunity given by detectors like the Fermi satellite. Because we are able to turn MAGIC within 20 seconds towards whatever source on the sky, we are very keen to react to targets of opportunities related to fast transients in the Universe, in particular gamma ray bursts.

Did you catch a burst during the explosion?

Not yet, unfortunately. A couple of times, we were really unlucky. Sometimes the gamma ray burst came in a bit of a wrong position, sometimes it came late in the day and so on. But we are in the limit of sensitivity and always hoping for the right burst.>>

Does very-high-energy gamma astrophysics belong to physics or to astronomy?

The history is full of cases in which the interplay between the two sciences has been the key for the advancement of science, I am thinking to the Greek philosophers, of Galilei and Newton, and Einstein. I believe this can be such a case. Modern gamma-ray astrophysics is such a frontier science that it cannot be properly classified into physics or astronomy: it is at the edge of both.
Will the Cherenkov Telescope Array (CTA) made by many telescopes be the natural next step?

I think CTA is important and it will be done. I still think that we have to take the maximum profit of what we have and move on to CTA through a prototyping phase, which increases step by step the power of the existing detectors.

What’s the role of international collaboration for a project like this?

Before doing this job I was at CERN for six years in a very international environment. I believe that worldwide collaboration in the 21st century is the only way to go. The size of the projects are so enormous that it needs a worldwide collaboration. In a sense, CTA is becoming the world project for very high energy cosmic ray physics.

What’s your advice to any student considering a career in physics?

I would recommend to be very careful to pursue a career in physics in an interdisciplinary culture, and with care to a strong mathematical basis. I mean in such a way that one can react fast to changes. I can not tell what will be the main drivers of physics in 20 or 30 years from now. But I am sure that physics will be always among the great actors of science

Submitted by Dirk Lorenzen (Germany)

MAGIC telescopesTwo magic telescopes

MAGIC is a system of two telescopes located at the Roque de los Muchachos Observatory on La Palma, one of the Canary Islands. MAGIC detects particle showers released by gamma rays, using Cherenkov radiation. With a diameter of 17 meters for the reflecting surface, these telescopes are the largest in the world of their kind. The first telescope started in 2004. A second telescope was added and started taking data in July 2009.

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